08 Impreza 2.5i

[DoubleApex]

So I've been doing a bit of research around here for the last few months and got around to joining. My car is a 2008 Subaru Impreza 2.5i with 93,000 miles on it. About 1,000 miles ago I did an oil change with Pennzoil Platinum 5w30 after all the good talk about it on these forums. I had been running M1 synthetic 5w30 since I got the car new doing roughly 7.5k oci which is what the manual calls for except under severe driving conditions it should be replaced every 3,750 miles or 3 3/4 months. The car doesn't use up any oil but has some bad knock in cold weather until it warms up, which I've also researched and is pretty normal among Subaru's but the sound worries me a bit.

So I believe I may actually fall under the severe driving conditions and was wondering what people thought. I drive my car for work and have a 15-20 mile commute depending on where I want to start my day, traveling most of the way going 40-50 mph. Once at work I typically cold start my car and drive 1-2 miles, 3-4 different times during the day in an area with a lot of traffic lights. I live in CT so I typically see temps from 0-100 during the year.

So should I start changing my oil every 3,750 or maybe go to a 5k oci? Should I stick with Pennzoil Platinum 5w30?

 

[charbaby]

No, I don't think so! Your commute to and from work(15-20 miles) should burn off any polutants from the short trips of your mid day. But, a used oil analysis may be in order and 5K miles would be the minimum that I'd run any oil. Maybe 6K in your situation using very well respected synthetic oils.

 

[Rolla07]

Pennzoil Platinum 5w30 is a good oil. I doubt shorter intervals will change cold knock. Why not try a 0w30? Might be a bit lighter on startup. I think your 7500k mile interval is fine.

 

[Wheel]

This may be the piston slap that many Subarus have, especially in cold weather. Different oils may may it quieter, but it is likely the short piston skirt causing the noise. My old Outback did this for the 15 years I had it, and my current Legacy does as well. There are many threads on legacygt.com about this, and clips on youtube of it as well.
I'd find an oil brand that mutes it as much as you can find, and forget about it. (If indeed it is piston slap)

 

[FutureDoc]

That is "Genuine Subaru Piston Slap". It is completely normal. I would not go chasing a oil to fix the "slap"... none really exist. Some say lighter oils, some say heavier, it is always a subjective choice. The slap will not harm you car and when it warms up, it should disappear.

Do a used oil analysis but I bet the PP/M1 is fine for 7500 miles. You driving pattern that you described would be "normal" in my book.